chemistry in DARS Karin Frjd Why DARS? Enabling detailed chemistry - - PowerPoint PPT Presentation

Reactive flows and complex chemistry in DARS

Karin Fröjd

Enabling detailed chemistry in your CAE simulations

• Take the right design choices, including chemical effects
• Faster and cheaper design cycles
• Evaluation of entirely new designs

Why DARS?

What is DARS Basic

TM?

Chemistry analyses Mechanism reduction Idealized reactors

– Ignition delay time – Emission production – Flame speed calculations

Library generation 1D & 0D PDF models for in-cylinder combustion and aftertreatment Standalone software for 0D and 1D analyses of chemical reactions DAR ARS S Bas asic v2.10 0 releas ased! !

• Focus

s on libr brar ary gene neration tion fo for r STAR AR-CC CCM+ M+ an and STAR-CD CD

Import any mechanism in DARS Basic Analyse the chemistry in reactors and flames Understand reaction pathways through species flow analysis

Chemistry analysis

Igniti tion dela lay y times s as functi ction of temperatu rature re for r n-hepta tane n-hepta tane deco composit sitio ion CO producti ction in fuel rich ch combusti stion of n-hepta tane

To avoid large CPU times the mechanism can be reduced Mechanism reduction through necessity analysis Visual analysis of the reaction scheme through flow analysis Steady state reduction through life- time analysis

Mechanism reduction

Flow analysis for n-heptane decomposition

Mechanism Reduction through necessity analysis

Flow + sensitivity analysis used to detect the most unnecessary species in the mechanism Workflow: – Read detailed reaction scheme – Run relevant reactor conditions, with necessity analysis turned

• n.

– Let DARS remove species with necessity lower than your defined threshold value – Check mechanism validity through rerun of relevant reactor conditions 6

Mechanism reduction panel – choose reduction limit here DARS workbench – read mechanism, constant pressure and reduce mechanism modules

DARS standard chemistry mechanisms

– n-heptane – TRF (n-heptane/toluene) – PRF (n-heptane/iso-octane) – Natural gas

Collaboration with prof. Lu, Univ. of Connecticut

– n-dodecane – PRF (n-heptane/iso-octane) – Biodiesel – DME – Ethanol – Natural gas

Any CHEMKINTM formatted mechanism from literature can be used

Chemistry mechanisms

Flow analysis for n-heptane decomposition

1D channel model in DARS Basic

– Thin film layer approach - transport to washcoat calculated – Surface chemistry in washcoat layer – Gas phase chemistry in gas – Detailed or global chemistry can be used. – Any CHEMKIN format chemistry can be used.

DARS Basic - catalyst

washcoat Monolith wall

DARS Basic - catalyst

DARS Basic - catalyst

Save time by analysing chemical reactions in 1D before employing full CFD

– Is detailed chemistry needed for the CFD calculation? – Can a reduced scheme be used? – Optimization of chemistry parameters for reduced schemes.

Study emission conversion as function of

– Catalyst length – Exhaust gas temperature – Exhaust species composition

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200 400 600 800 1,000 1,200

• 30

20 70 120 170 220 Temperature [K] / Concentration (ppm) Time [min]

InletT[K] NO_GasOut NO2_GasOut N2O_GasOut NH3_GasOut

Ammonia SCR for a temperature ramp C3H6 inhibition of NO oxidation under lean conditions in Nox- storage catalyst

With DARS Basic v2.10 you can export

– FGM libraries – Soot libraries – ECFM-3Z single/dual fuel libraries – ECFM-CleH single/dual fuel libraries – PVM-MF single/dual fuel libraries

Straightforward parameter specification, designed for each library type

– Set up a full library calculation in less than 10 minutes.

Paralellization for efficient library generation

Library generation

FGM libraries

Simulate combustion accurately and fast

– DARS Basic can now export FGM libraries for STAR-CCM+ – For non-premixed and partially premixed combustion

Explore combustion of any fuel/oxidant mixture

– Any CHEMKIN™ format chemistry can be used

Improve species prediction

– Choose species for postprocessing in STAR-CCM+.

Igniti tion proce cess ss for n-hepta tane combusti stion at vario rious s equiva vale lence ce ratio ios CO mass s fracti ction durin ing n-hepta tane combusti stion at vario rious s equiva vale lence ce ratio ios

Soot source term libraries

DARS Basic v2.10 can export Soot sectional and moment method libraries

– Flamelets are used to capture turbulence-chemistry interaction

Specify ranges and grid in T, P, EGR and scalar dissipation rate Library set up ~ 10 min Library calculation: ~ 40 h on 16 cores for single fuel library

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The gas s composit sitio ion panel, l, use sed for r specif cifica icati tion of parame ramete ter r range and grid id Soot t surfa face ce growth wth as functi ction of mixtu ture re fracti ction for r n-hepta tane combusti stion at vario rious s strain rate tes

Thank you for your attention

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